Tonight at 9/8c, CBS’ NCIS: Los Angeles launches into the final three episodes of Season 4, opening with an hour that pits Callen against Hetty, then lightening things up by ruffling Kensi’s feathers, and closing the season with events that Shane Brennan can’t use the word “dark” often enough to describe. Here, the showrunner previews all that’s to come.

TVLINE | Do these next couple of episodes feed the finale, or is the finale almost standalone?
Tensions are mounting and things are happening that ultimately will lead to the most powerful finale episode we’ve done — and we’ve done some pretty powerful ones, so that’s saying something — and the darkest by a long, long way. It really ends in a scary place. It is quite dark.

TVLINE | But first things first: Talk about this week’s episode, “Raven & the Swans,” and how guest star Andrea Roth (Rescue Me) fits in.
We will see a little bit of Hetty that we hinted at in the past, and [Andrea’s character] is a part of that past. What we have in this episode is something we haven’t seen before. We know that Callen and Hetty have quite an affinity for each other, that they have a special relationship based on the fact that Hetty was responsible for looking after Callen as a child, putting him into foster homes and trying to shape him. What this episode reveals is another part of that history, but it’s more what Callen learns about Hetty that is the revelation. In fact, there is a moment between Callen and Hetty that is explosive. It’s angry. We haven’t seen them like this before. Callen quite literally attacks her. It is quite a confrontational scene that emotionally impacts both of them.

TVLINE | And next week, in the episode “Parley” — is that Jeananne Goossen (CSI: NY) playing Deeks’ “source”?
She’s playing the very seductive Monica, yes. This is an episode that puts Deeks undercover with a beautiful woman, and Kensi would never be jealous of something like that, ever. Not gonna happen. But of course there is some jealousy, and of course Deeks — being the “Method” undercover agent that he is — tries to play it as real as possible. It puts pressure on their relationship and at the same time it lights the fuse for the finale, with the return of Sidorov (played by Sons of Anarchy’s Timothy V. Murphy).

And just to go back to “Raven & the Swan”: People who love the Kensi/Deeks relationship really shouldn’t miss that one. While it very much is Hetty and Callen, there is an absolutely hilarious scene with Kensi and Deeks at the center of it. In fact, Kensi and Deeks fans have a bit of a three-parter coming up, in the sense that there’s a lot of fun in “Raven & the Swan,” there’s a moment of potential jealousy with Deeks undercover with Monica, and in the finale is a moment that fans cannot miss, something we’ve been toying with and teasing for three seasons. It’s a moment people will want to DVR and rewatch very closely.

TVLINE | Well speaking of the season finale, “Descent,” Barrett Foa told us it features a veritable League of Supervillains.
It is exactly that. In addition to Sidorov, The Chameleon (Highlander‘s Christopher Lambert) makes a very surprising return, having last been seen happily getting into a car with the Iranians that he had betrayed — and let’s just say that he’s not the man he used to be. The episode is a high-stakes conclusion of the missing nukes [storyline], and it plays out around the world. The first 30 seconds should not be missed. It’s pretty astonishing what happens, and from there it ramps up even more.

TVLINE | And Hetty shuffles partners again?
She does, and anytime you see Deeks and Sam working together, you know there’s going to be friction. Ultimately this episode plays out in a way that puts these two together in a life-threatening situation that tests their trust. And as I’ve said, it leads to this very, very dark — and I mean dark — conclusion, with Deeks and Sam at the center of it. We also see the return of Sam’s wife Michelle and all the issues that taunted Sam regarding her working undercover. The jeopardy that one of the characters is put into springs directly from that.

TVLINE | So, we should watch for potential fatalities?
There are potentially two, and they’re not subsidiary characters. It really is quite a stunning end to a stunning episode that starts from a very powerful place. Things kind of unravel for the team, because the best laid plans sometimes don’t go so well. And when you’re dealing with this kind of international terrorism, sometimes you end up making unlikely alliances!